The invention is based on a linear unit. Units are suitable, for example, for seizing an object and displacing it with the aid of electromagnetic actuating drives in one or more predetermined directions by certain amounts, entered in advance. Since the displacement speeds are comparatively high, it is necessary to keep the mass of the moving tool support of the unit and of the rotor of the linear motor connected to it as small as possible, in order that their movements can be damped promptly and effectively. Thus, it may be ensured that the support is also actually stopped as well at the point at which the standstill is required. Therefore, materials or material combinations which meet the requirement for lowest possible mass, great rigidity and wear resistance are used for production of the tool supports. Hollow profiles of aluminium or a composite of aluminum and steel, produced in the extrusion process, have proved particularly suitable, the basic body consisting of aluminium and the bearing surfaces of steel strips.
Electromagnetically driven linear motors with a gear rack of magnetically conductive material as motor rotor and a magnetizable motor stator are known in large number. Such a motor is described, for example, in German Offenlegungsschrift No. 2,247,509. The moving element of the motor consists of a solid, magnetic bar, which may have round or rectangular cross-section and is provided on its outside surface with one or more rows of teeth of the same pitch. Opposite each row of teeth lie several pole masses, which are provided with windings and at the same time each have a toothing. The mutually facing surfaces of the rows of teeth lie in two parallel planes with an intermediate space, which forms the pole gap. The bar forming the moving element may, on account of the principle, be made only so thick that the magnetic lines of flux are able to penetrate it without difficulties.
It would be obvious simply to fit the known or a similarly designed linear motor to the holder of the tool support and connect its gear rack to the tool support in such a way that the gear rack is the driving element and the tool support is the driven element. Such a solution would be elaborate inasmuch as both the gear rack and the tool support require a precision bearing of their own and the linear unit as a whole would have a large volume.